Powder application apparatus and method of operating a powder application apparatus

ABSTRACT

A powder application apparatus is provided for use in a device for manufacturing work pieces by exposing powder layers to electromagnetic radiation or particle radiation. The powder application apparatus comprises a first powder storage provided in a first part of the powder application apparatus and configured to receive and store raw material powder. The powder application apparatus further comprises a first powder supply channel provided in a second part of the powder application apparatus and configured to discharge raw material powder from the first powder storage onto a carrier located below the apparatus. A first channel opening/closing element is configured to be moved between a first position to allow the discharge of raw material powder from the first powder storage onto the carrier, and a second position in which the discharge of raw material powder from the first powder storage onto the carrier is presented.

TECHNICAL FIELD

The present invention relates to a powder application apparatus for usein a device for manufacturing work pieces by exposing powder layers toelectromagnetic radiation or particle radiation. Further, the presentinvention relates to a method of operating such a powder applicationapparatus.

BACKGROUND

It is known to manufacture complex three-dimensional work pieces byselectively exposing powder layers to electromagnetic radiation orparticle radiation. In such manufacturing approaches, a raw materialpowder layer of a metallic or a ceramic material is deposited onto acarrier. Then, the raw material powder layer is selectively exposed toirradiation (e.g. to a laser beam). The positions of the powder areasselectively exposed to irradiation usually differ from raw materialpowder layer to raw material powder layer and depend on a targetgeometry of the three-dimensional work piece to be manufactured. Due tothe irradiation, particles of raw material powder located within theirradiated areas melt or sinter, thereby transforming the parts of theraw material powder layer located within the irradiated areas intocorresponding solid material structures. After having generated thesolid material structures, a further raw material powder layer isdeposited onto the carrier (i.e. deposited onto the overall solidmaterial structure generated so far), and is exposed to irradiation incorresponding selected areas, and so on.

FIG. 1 schematically shows a conventional powder application apparatus10. The powder application apparatus 10 comprises a powder storage 12provided in a first part of the powder application apparatus andconfigured to receive and store raw material powder. Further, the powderapplication apparatus 10 comprises a powder supply channel 14 providedin a second part of the powder application apparatus 10 and configuredto discharge raw material powder from the powder storage 12 onto acarrier 16 located below the powder application apparatus 10. A channelopening/closing mechanism 18 which is provided in the powder supplychannel 14 comprises a moving element configured to be moved between afirst position in which the moving element allows the discharge of rawmaterial powder from the powder storage 12 onto the carrier 16, and asecond position in which the moving element prevents the discharge ofraw material powder from the powder storage 12 onto the carrier 16. Thechannel opening/closing mechanism 18 usually comprises electric motorswhich drive the moving element between the first and the secondposition.

SUMMARY

It is an object of the present invention to provide an alternativepowder application apparatus which is suitable for use in a device formanufacturing work pieces by exposing powder layers to electromagneticradiation or particle radiation. Further, it is an object of the presentinvention to provide a method of manufacturing work pieces by exposingpowder layers to electromagnetic radiation or particle radiation usingsuch an alternative powder application apparatus.

According to an aspect of the present invention, a powder applicationapparatus for use in a device for manufacturing work pieces by exposingpowder layers to electromagnetic radiation or particle radiation isprovided. The powder application apparatus comprises a first powderstorage provided in a first part of the powder application apparatus andconfigured to receive and store raw material powder. The powderapplication apparatus further comprises a first powder supply channelprovided in a second part of the powder application apparatus andconfigured to discharge raw material powder from the first powderstorage onto a carrier located below the apparatus. Further, a firstchannel opening/closing element is provided in the first powder supplychannel, the first channel opening/closing element being configured tobe moved between a first position in which the first channelopening/closing element allows the discharge of raw material powder fromthe first powder storage onto the carrier, and a second position inwhich the first channel opening/closing element prevents the dischargeof raw material powder from the first powder storage onto the carrier.The first channel opening/closing element is configured to be movedbetween the first and the second position by means of an externalmechanical force acting on the first channel opening/closing element,the external mechanical force being caused by abutting the first channelopening/closing element against a stopper of the device formanufacturing work pieces when moving the powder application apparatusover the carrier.

The term “external mechanical force” in the context of the presentapplication should designate a mechanical force which acts on the firstchannel opening/closing element of the powder application apparatus from“outside” of the powder application apparatus. Specifically, theexternal mechanical force is caused by the interaction of the firstchannel opening/closing element with the stopper of the device formanufacturing work pieces when the powder application apparatus is movedover the carrier. In particular, upon movement of the powder applicationapparatus over the carrier in one direction, the interaction of thefirst channel opening/closing element with the stopper may generate anexternal mechanical force which acts on the first channelopening/closing element so as to cause a movement of the first channelopening/closing element in an opposite direction.

An advantageous effect of such a powder application apparatus is thatthe first channel opening/closing mechanism has a simple structure,since it is wholly mechanically driven, i.e. no electric motors areneeded as driving means. This significantly reduces the weight of thepowder application apparatus which again makes it possible to increasethe speed/acceleration characteristics of movements of the powderapplication apparatus. Also, there is no need to provide electricalconnections which provide the powder application apparatus withelectrical energy from outside in order to drive the electric motors.Further, there is no need to track the position of the powderapplication apparatus in order to discharge the raw material powder atthe right position since it is automatically ensured that the rawmaterial powder is discharged in the desired area (an area in front of aleveling slider the structure and function of which will be explained inmore detail in the following).

According to an embodiment, in one of the first and the second position,the first channel opening/closing element projects from a side surfaceof a housing of the powder application apparatus. In the other one ofthe first and the second position, the first channel opening/closingelement may not project from the side surface of the housing of thepowder application apparatus, or may project less or further from theside surface of the housing of the powder application apparatus.

The first channel opening/closing element may, for example, be a platemember movable in a horizontal direction between the first and thesecond position, wherein, in one of the first and the second position, aside surface of the plate member may project from the side surface ofthe housing of the powder application apparatus, and wherein, in theother one of the first and the second position, the side surface of theplate member may be aligned with the side surface of the housing of thepowder application apparatus, or may project less or further from theside surface of the housing of the powder application apparatus. Forexample, the first channel opening/closing element might be providedwith an opening which is aligned with the first powder supply channelwhen the first channel opening/closing element is disposed in its firstposition such that raw material powder from the first powder storage canbe discharged onto the carrier through the opening.

Alternatively, the first channel opening/closing element may comprise apivotable blade which, in the second position of the firstopening/closing element, is adapted to receive raw material powderdischarged from the first powder storage, but to prevent the rawmaterial powder from being applied onto the carrier. Further, thepivotable blade may be adapted to pivot around a pivot axis in order todischarge the raw material powder onto the carrier, when an externalmechanical force acts on the first channel opening/closing element, theexternal mechanical force in particular being caused by abutting thefirst channel opening/closing element against a stopper of the devicefor manufacturing work pieces when moving the powder applicationapparatus over the carrier.

The powder application apparatus may further comprise a first springelement connected to the first channel opening/closing element and thepowder application apparatus such that the spring element causes a forcewhich automatically pushes the first channel opening/closing elementfrom the first position into the second position as soon as the firstchannel opening/closing element no longer abuts against the stopper. Thestopper then merely serves to push the first channel opening/closingelement into its first position, whereas the spring serves to move thefirst channel opening/closing element into its second position. Further,the device for manufacturing work pieces may comprise two stoppers. Afirst stopper then may serve to interact with the first channelopening/closing element so as to move the first channel opening/closingelement into its first position, whereas a second stopper may serve tointeract with the first channel opening/closing element so as to movethe first channel opening/closing element into its second position. Forexample, the two stoppers may be provided in the region of opposing sidesurfaces of the housing of the powder application apparatus.

The powder application apparatus may further comprise a second powderstorage provided in a first part of the powder application apparatus andconfigured to receive and store raw material powder, a second powdersupply channel provided in a second part of the powder applicationapparatus and configured to discharge raw material powder from thesecond powder storage onto the carrier located below the apparatus, anda second channel opening/closing element provided in the second powdersupply channel and being configured to be moved between a first positionin which the second channel opening/closing element allows the dischargeof raw material powder from the second powder storage onto the carrier,and a second position in which the second channel opening/closingelement prevents the discharge of raw material powder from the secondpowder storage onto the carrier. The second channel opening/closingelement may be configured to be moved between the first and the secondposition by means of an external mechanical force acting on the secondchannel opening/closing element, the external mechanical force beingcaused by abutting the second channel opening/closing element against astopper of the device for manufacturing work pieces when moving thepowder application apparatus over the carrier.

A powder application apparatus which comprises two powder storages maybe loaded with two different types of raw material powders. Further, aswill be described in more detail below, power contained in the firstpowder storage may be applied onto the carrier when moving the powderapplication apparatus in a first direction, while power contained in thesecond powder storage may be applied onto the carrier when moving thepowder application apparatus in a second direction opposite to the firstdirection. Further, a powder application apparatus which comprises afirst and a second channel opening/closing element preferably isemployed in a device for manufacturing work pieces which is equippedwith two stoppers such that the first device channel opening/closingelement may interact with a first stopper, while the second channelopening/closing element may interact with a second stopper in order tomove the first and the second channel opening/closing element betweenthe respective first and second positions.

The second channel opening/closing element may be configured asdescribed above in connection with the first channel opening/closingelement, i.e. in one of the first and the second position, the secondchannel opening/closing element may project from a side surface of ahousing of the powder application apparatus. In the other one of thefirst and the second position, the second channel opening/closingelement may not project from the side surface of the housing of thepowder application apparatus, or may project less or further from theside surface of the housing of the powder application apparatus.

Like the first channel opening/closing element, also the second channelopening/closing element may, for example, be a plate member movable in ahorizontal direction between the first and the second position, wherein,in one of the first and the second position, a side surface of the platemember may project from the side surface of the housing of the powderapplication apparatus, and wherein, in the other one of the first andthe second position, the side surface of the plate member may be alignedwith the side surface of the housing of the powder applicationapparatus, or may project less or further from the side surface of thehousing of the powder application apparatus. For example, the secondchannel opening/closing element might be provided with an opening whichis aligned with the second powder supply channel when the second channelopening/closing element is disposed in its first position such that rawmaterial powder from the second powder storage can be discharged ontothe carrier through the opening.

Alternatively, the second channel opening/closing element may comprise apivotable blade which, in the second position of the second channelopening/closing element, is adapted to receive raw material powderdischarged from the second powder storage, but to prevent the rawmaterial powder from being applied onto the carrier. Further, thepivotable blade may be adapted to pivot around a pivot axis in order todischarge the raw material powder onto the carrier, when an externalmechanical force acts on the second channel opening/closing element, theexternal mechanical force in particular being caused by abutting thesecond channel opening/closing element against a stopper of the devicefor manufacturing work pieces when moving the powder applicationapparatus over the carrier.

The powder application apparatus may further comprise a second springelement connected to the second channel opening/closing element and thepowder application apparatus such that the spring element causes a forcewhich automatically pushes the second channel opening/closing elementfrom the first position into the second position as soon as the secondchannel opening/closing element no longer abuts against the stopper. Thestopper then merely serves to push the second channel opening/closingelement into its first position, whereas the spring serves to move thesecond channel opening/closing element into its second position.

Additionally or alternatively thereto, the first channel opening/closingelement and the second channel opening/closing element, however, alsomay be formed integrally with each other, i.e. a single component mayform the first and the second channel opening/closing element. Forexample, the first channel opening/closing element and the secondchannel opening/closing element may be formed by a plate member whichmay be movable in a horizontal direction. The plate member may beprovided with two openings which may be brought into alignment with thefirst and the second powder supply channel, respectively such that rawmaterial powder from the first and the second powder storage,respectively, can be discharged onto the carrier through the respectiveopening.

The first and the second channel opening/closing element may beconfigured such that both, the first and the second channelopening/closing element, can be simultaneously positioned in a fillingposition, in which they prevent the discharge of raw material powderfrom the first and the second powder storage onto the carrier. When thefirst and the second channel opening/closing element are disposed intheir filling position, the first and the second powder storage can befilled with a desired amount of powder, while the discharge of saidpowder onto the carrier is prevented. When disposed in its fillingposition, the first channel opening/closing element may project from afirst side surface of a housing of the powder application apparatus.Similarly, when disposed in its filling position, the second channelopening/closing element may project from a second side surface of ahousing of the powder application apparatus which is disposed oppositefrom the first side surface of a housing of the powder applicationapparatus.

Further, the first and the second channel opening/closing element may beconfigured such that a combined movement of the first and the secondchannel opening/closing element from their filling position in a firstmoving direction causes the first channel opening/closing element tomove into its first position, in which it allows the discharge of rawmaterial powder from the first powder storage onto the carrier, andsimultaneously causes the second channel opening/closing element to moveinto its second position, in which it prevents the discharge of rawmaterial powder from the second powder storage onto the carrier.

When the first channel opening/closing element is disposed in its firstposition, the first channel opening/closing element may project furtherfrom the first side surface of the housing of the powder applicationapparatus than in its filling position. The second channelopening/closing element, when being disposed in its second position,however, may project less from the second side surface of the housing ofthe powder application apparatus than in its filling position or mayeven be aligned with the second side surface of the housing of thepowder application apparatus. The combined movement of the first and thesecond channel opening/closing element may be achieved by a movement ofthe powder application apparatus in a second moving direction oppositeto the first moving direction and the abutment of the second channelopening/closing element against a second stopper associated with thesecond channel opening/closing element.

Moreover, the first and the second channel opening/closing element maybe configured such that a combined movement of the first and the secondchannel opening/closing element from the filling position in a secondmoving direction causes the first channel opening/closing element tomove into its second position, in which it prevents the discharge of rawmaterial powder from the first powder storage onto the carrier, andsimultaneously causes the second channel opening/closing element to moveinto its first position, in which it allows the discharge of rawmaterial powder from the second powder storage onto the carrier.

When the first channel opening/closing element is disposed in its secondposition, the first channel opening/closing element may project lessfrom the first side surface of the housing of the powder applicationapparatus than in its filling position or may even be aligned with thefirst side surface of the housing of the powder application apparatus.The second channel opening/closing element, when being disposed in itsfirst position, however, may project further from the second sidesurface of the housing of the powder application apparatus than in itsfilling position. The combined movement of the first and the secondchannel opening/closing element may be achieved by a movement of thepowder application apparatus in a first moving direction opposite to thesecond moving direction and the abutment of the first channelopening/closing element against a first stopper associated with thefirst channel opening/closing element. Further, as will be described inmore detail below, power contained in the first powder storage may bedistributed onto the carrier when moving the powder applicationapparatus in a first direction, while power contained in the secondpowder storage may be distributed onto the carrier when moving thepowder application apparatus in a second direction opposite to the firstdirection.

This configuration of the first and the second channel opening/closingelement allows a particularly efficient operation of the powderapplication apparatus. In a first step, the first and the second channelopening/closing element may positioned in their respective fillingpositions. This may be achieved, for example, by a suitable movement ofthe powder application apparatus over the carrier and a correspondinginteraction of the first or the second channel opening/closing elementwith the first or the second stopper. The first and the second powderstorage then may be filled while the first and the second channelopening/closing element prevent the discharge of powder onto thecarrier.

In a second step, the powder application apparatus may be moved over thecarrier in a first moving direction until the first channelopening/closing element abuts against the first stopper. Thereby thefirst and the second channel opening/closing element are moved in asecond moving direction opposite to the first moving direction until thefirst channel opening/closing reaches its second position, in which itstill prevents the discharge of raw material powder from the firstpowder storage onto the carrier, whereas the second channelopening/closing element is positioned in its first position, in which itallows the discharge of raw material powder from the second powderstorage onto the carrier.

Thereafter, the powder application apparatus may be moved over thecarrier in the second moving direction until the second channelopening/closing element abuts against the second stopper. Thereby thefirst and the second channel opening/closing element are moved in thefirst moving direction opposite to the second moving direction until thefirst channel opening/closing reaches its first position, in which itallows the discharge of raw material powder from the first powderstorage onto the carrier, whereas the second channel opening/closingelement is positioned in its second position, in which it prevents thedischarge of raw material powder from the second powder storage onto thecarrier. In this way, each time the powder application apparatus movesover the carrier, a powder layer can be generated, i.e. the powderapplication apparatus does not have to move over the carrier withoutgenerating a powder layer.

The first powder storage may extend along a plane being inclined withregard to a vertical plane coinciding with a longitudinal axis of thepowder application apparatus such that a distance between the verticalplane and the first powder storage increases when moving from a firstpart of the first powder storage to a second part of the first powderstorage. Further, the second powder storage may extend along a planebeing inclined with regard to the vertical plane of the powderapplication apparatus such that a distance between the vertical planeand the second powder storage increases when moving from a first part ofthe second powder storage to a second part of the second powder storage.

In this way, the volume of the first powder storage and the volume ofthe second powder storage are kept small which means that the amount ofraw powder material in the first powder storage/second powder storage isalso limited. This reduces the weight of the power applicationapparatus. On the other hand, since there is enough raw material powderin the first powder storage and the second powder storage for generatingtwo subsequent powder layers (one when moving the power applicationapparatus towards the second stopper using raw material powder from thesecond powder storage, and another one when moving the power applicationapparatus towards the first stopper using raw material powder from thefirst powder storage), no interruption of the powder application processis needed. It is sufficient to refill raw material powder into the firstpowder storage and into the second powder storage after two powderapplication cycles.

An inlet end of the first powder storage may comprise a plurality offirst inlets for receiving raw material powder, and an inlet end of thesecond powder storage may comprise a plurality of second inlets forreceiving raw material powder, wherein the first inlets are differentfrom the second inlets. In this way, it is possible to precisely fillthe same amount of raw material powder into the first powder storage andinto the second powder storage by making sure that the amount of rawmaterial powder received by the first inlets corresponds to that of thesecond inlets. This ensures that the thicknesses of the powder layerscan be controlled to be exactly the same. On the other hand, thisenables to fill a first powder material into the first powder storage,and to fill a second powder material into the second powder storagewithout having the danger that the different powder materials mix witheach other. Thus, sandwich layer structures of different powder materiallayers can be generated easily. The first inlets and the second inletsmay alternate with each other along a direction parallel to thelongitudinal axis of the powder application apparatus.

At a bottom surface of the powder application apparatus, a detachablyattached leveling slider may be provided. Thus, the leveling slider maybe exchanged easily on demand, depending on the kind of manufacturingprocess. The leveling slider serves to evenly distribute powder appliedonto the carrier from the first and/or the second powder storage over asurface of the carrier. Preferably, the leveling slider is arranged onthe powder application apparatus in such a position that the levelingslider, in a moving direction of the powder application apparatus overthe carrier, is disposed behind the powder supply channel through whichraw material powder is supplied onto the carrier. In a powderapplication apparatus comprising two powder storages and two powdersupply channels, the leveling slider preferably is arranged between thefirst and the second powder supply channel.

Between the first powder storage and the second powder storage, a spacemay be provided which extends, starting from a bottom surface of thepowder application apparatus, into the powder application apparatustowards a first part of the powder application apparatus. A holdingelement may be fitted into the space such that it is movable along avertical direction within the space, wherein a bottom surface of theholding element comprises the detachably attached leveling slider.

The vertical position of the holding element may be adjustable bymicrometer screws extending vertically through a top surface of thepowder application apparatus and through the space by actuating themicrometer screws at their top ends. In this way, a very simplemechanism is provided enabling to easily modify the vertical position ofthe detachably attached leveling slider.

According to an aspect of the present invention, in a method ofmanufacturing work pieces by exposing powder layers to electromagneticradiation or particle radiation using a powder application apparatus asdescribed above the first channel opening/closing element is movedbetween the first and the second position by means of an externalmechanical force acting on the first channel opening/closing element,the external mechanical force being caused by abutting the first channelopening/closing element against a stopper of the device formanufacturing work pieces when moving the powder application apparatusover the carrier.

The method may involve the use of a powder application apparatus whichfurther comprises a second powder storage provided in a first part ofthe powder application apparatus and configured to receive and store rawmaterial powder, a second powder supply channel provided in a secondpart of the powder application apparatus and configured to discharge rawmaterial powder from the second powder storage onto the carrier locatedbelow the apparatus, and a second channel opening/closing elementprovided in the second powder supply channel and configured to be movedbetween a first position in which the second powder supply channelallows the discharge of raw material powder from the second powderstorage onto the carrier, and a second position in which the secondpowder supply channel prevents the discharge of raw material powder fromthe second powder storage onto the carrier. The method then may furthercomprise the step of moving the second channel opening/closing elementbetween the first and the second position by means of an externalmechanical force acting on the second channel opening/closing element,the external mechanical force being caused by abutting the secondchannel opening/closing element against a stopper of the device formanufacturing work pieces when moving the powder application apparatusover the carrier.

The method may further comprise the step of simultaneously positioningboth, the first and the second channel opening/closing element in afilling position, in which they prevent the discharge of raw materialpowder from the first and the second powder storage onto the carrier.Further, both, the first and the second channel opening/closing element,may be moved from their filling position in a first moving direction soas to cause the first channel opening/closing element to move into itsfirst position, in which it allows the discharge of raw material powderfrom the first powder storage onto the carrier, and to simultaneouslycause the second channel opening/closing element to move into its secondposition, in which it prevents the discharge of raw material powder fromthe second powder storage onto the carrier. Finally, it is alsoconceivable to move both, the first and the second channelopening/closing element from the filling position in a second movingdirection so as to cause the first channel opening/closing element tomove into its second position, in which it prevents the discharge of rawmaterial powder from the first powder storage onto the carrier, and tosimultaneously cause the second channel opening/closing element to moveinto its first position, in which it allows the discharge of rawmaterial powder from the second powder storage onto the carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description, exemplary embodiments of the presentinvention will be explained, wherein

FIG. 1 shows a schematic cross-sectional illustration of a conventionalpowder application apparatus;

FIGS. 2 a, 2 b show a schematic cross-sectional illustration of a powderapplication apparatus according to an embodiment of the presentinvention;

FIGS. 3 a-3 c show a perspective-cross-sectional illustration of apowder application apparatus according to an embodiment of the presentinvention;

DETAILED DESCRIPTION

In the embodiments explained in the following, identical/similar areas,parts or elements are denoted by identical reference numerals.

As shown in FIGS. 2 a and 2 b, a powder application apparatus 10′according to a first embodiment of the present invention is provided foruse in a device for manufacturing work pieces by exposing powder layersto electromagnetic radiation or particle radiation. The powderapplication apparatus 10′ comprises a first powder storage 12 a providedin a first, i.e. an upper part 20 of the powder application apparatus10′ and configured to receive and store raw material powder via a powderinlet 22. The powder application apparatus 10′ further comprises a firstpowder supply channel 14 a provided in a second, i.e. a lower part 24 ofthe powder application apparatus 10′ and configured to discharge rawmaterial powder from the first powder storage 12 a onto a carrier 16located below the apparatus.

Further, the powder application apparatus 10′ comprises a first channelopening/closing element 26 a which is provided in the first powdersupply channel 14 a, the first channel opening/closing element 26 abeing configured to be moved between a first position (see FIG. 2 b) inwhich the first channel opening/closing element 26 a allows thedischarge of raw material powder from the first powder storage 12 a ontothe carrier 16, and a second position (see FIG. 2 a) in which the firstchannel opening/closing element 26 a prevents the discharge of rawmaterial powder from the first powder storage 12 a onto the carrier 16.The first channel opening/closing element 26 a is configured to be movedbetween the first and the second position by means of an externalmechanical force acting on the first channel opening/closing element 26a, the external mechanical force being caused by abutting the firstchannel opening/closing element 26 a against a first stopper 28 a of thedevice for manufacturing work pieces when moving the powder applicationapparatus 10′ over the carrier 16. The first stopper 28 a is formedseparate from the carrier 16. For example, the first stopper 28 a may bemounted to a sidewall of a housing of the device for manufacturing workpieces (not shown in the drawings).

That is, in the second position (which is the default position), thefirst channel opening/closing element 26 a projects from a side surface34 a of a housing 36 of the powder application apparatus 10′ and a firstend 30 of the first channel opening/closing element 26 a does not abutagainst the first stopper 28 a. However, when moving the powderapplication apparatus 10′ along a first direction D1 over the carrier16, the first end 30 of the first channel opening/closing element 26 aabuts against the first stopper 28 a. In this way, an externalmechanical force is generated which acts on the first end 30 and causesthe first channel opening/closing element 26 a to move within the powderapplication apparatus 10′ along a second direction D2 opposite to thefirst direction D1. In this way, the first channel opening/closingelement 26 a is moved from its second position into its first position.When the first channel opening/closing element 26 a is disposed in thefirst position, the first channel opening/closing element 26 a no longerprojects from the side surface 34 a of the housing 36 of the powderapplication apparatus 10′. Instead, the first end 30 is aligned with theside surface 34 a of the housing 36 and. An opening area 32 of the firstchannel opening/closing element 26 a is located within the first powdersupply channel 14 a, thereby forming a passage between the first powderstorage 12 a and the second part of the first powder supply channel 14a, whereas, in the second position of the first channel opening/closingelement 26 a, the opening area 32 is located outside the first powdersupply channel 14 a.

The powder application apparatus 10′ further comprises a spring element(not shown) which is connected to the first channel opening/closingelement 26 a and the powder application apparatus 10′ such that thespring element causes a force which automatically pushes the firstchannel opening/closing element 26 a from the first position into thesecond position as soon as the first channel opening/closing element 26a no longer abuts against the stopper. The stopper 28 a thus merelyserves to push the first channel opening/closing element 26 a into itsfirst position, whereas the spring serves to move the first channelopening/closing element 26 a into its second position.

The powder application apparatus 10′ has a simple structure since thefirst channel opening/closing element 26 a is wholly mechanicallydriven, i.e. no electric motors are needed as driving means. Thus, theweight of the powder application apparatus 10′ is low. This makes itpossible to increase the speed/acceleration of movement of the powderapplication apparatus 10′ over the carrier. The amount of powder appliedonto the carrier 16 is controlled by suitably controlling the amount ofpowder introduced into the first powder storage 12 a. In particular, thefirst powder storage 12 a is filled with an amount of powder thatcorresponds to the amount of powder which is necessary to apply the nextpowder layer onto the carrier 16 plus a predetermined excess powderamount which serves to prevent underfeeding of powder onto the carrier16.

FIGS. 3 a to 3 c show a second embodiment of a powder applicationapparatus 10″. The powder application apparatus 10″ comprises a firstpowder storage 12 a provided in a first, i.e. an upper part 20 of thepowder application apparatus 10″ and configured to receive and store rawmaterial powder via a powder inlet 22. The powder application apparatus10″ further comprises a first powder supply channel 14 a provided in asecond, i.e. a lower part 24 of the powder application apparatus 10″ andconfigured to discharge raw material powder from the first powderstorage 12 a onto a carrier 16 located below the powder applicationapparatus 10″.

Further, a first channel opening/closing element 26 a is provided in thefirst powder supply channel 14 a, the first channel opening/closingelement 26 a being configured to be moved between a first position inwhich the first channel opening/closing element 26 a allows thedischarge of raw material powder from the first powder storage 12 a ontothe carrier 16, and a second position in which the first channelopening/closing element 26 a prevents the discharge of raw materialpowder from the first powder storage 12 a onto the carrier 16.

The powder application apparatus 10″ further comprises a second powderstorage 12 b provided in the first part 20 of the powder applicationapparatus 10″ and being configured to receive and store raw materialpowder via the powder inlet 22. A second powder supply channel 14 b isprovided in the second part 24 of the powder application apparatus 10″and configured to discharge raw material powder from the second powderstorage 12 b onto the carrier 16.

A second channel opening/closing element 26 b is provided in the secondpowder supply channel 14 b, the second channel opening/closing element26 b being configured to be moved between a first position in which thesecond channel opening/closing element 26 b allows the discharge of rawmaterial powder from the second powder storage 12 b onto the carrier 16,and a second position in which the second channel opening/closingelement 26 b prevents the discharge of raw material powder from thesecond powder storage 12 b onto the carrier 16.

The first and the second channel opening/closing element 26 a, 26 b areformed integrally with each other. Further, the first and the secondchannel opening/closing element 26 a, 26 b are configured such thatboth, the first and the second channel opening/closing element 26 a, 26b, can be simultaneously positioned in a filling position, in which theyprevent the discharge of raw material powder from the first and thesecond powder storage 12 b onto the carrier 16 (see FIGS. 3 b and 3 c).When the first and the second channel opening/closing element 26 a, 26 bare disposed in their filling position, the first and the second powderstorage 14 a, 14 b can be filled with a desired amount of powder, whilethe discharge of said powder onto the carrier 16 is prevented. Whendisposed in its filling position, the first channel opening/closingelement 26 projects from a first side surface 34 a of a housing 36 ofthe powder application apparatus 10″. Similarly, when disposed in itsfilling position, the second channel opening/closing element 26 bprojects from a second side surface 34 b of the housing 36 of the powderapplication apparatus 10″, the second side surface 34 b being disposedopposite from the first side surface 34 a.

The first channel opening/closing element 26 a is configured to be movedbetween its first and its second position by means of an externalmechanical force acting on the first channel opening/closing element 26a, the external mechanical force being caused by abutting the firstchannel opening/closing element 26 a against a first stopper 28 a of thedevice for manufacturing work pieces when moving the powder applicationapparatus 10″ over the carrier 16 in a first moving direction D1 and byabutting the first channel opening/closing element 26 a, via the secondchannel opening/closing element 26 b, against a second stopper 28 b ofthe device for manufacturing work pieces when moving the powderapplication apparatus 10″ over the carrier 16 in a second movingdirection D2.

Similarly, the second channel opening/closing element 26 b is configuredto be moved between its first and its second position by means of anexternal mechanical force acting on the second channel opening/closingelement 26 b, the external mechanical force being caused by abutting thesecond channel opening/closing element 26 b against the second stopper28 b of the device for manufacturing work pieces when moving the powderapplication apparatus 10″ over the carrier 16 in the second movingdirection D2 and by abutting the second channel opening/closing element26 b, via the first channel opening/closing element 26 a, against thefirst stopper 28 a of the device for manufacturing work pieces whenmoving the powder application apparatus 10″ over the carrier 16 in thefirst moving direction D1. The first and the second stopper 28 a, 28 bare formed separate from the carrier 16. For example, the first and thesecond stopper 28 a, 28 b may be mounted to opposing sidewalls of ahousing of the device for manufacturing work pieces (not shown in thedrawings).

A combined movement of the first and the second channel opening/closingelement 26 a, 26 b from their filling position in the first movingdirection D1 due to a movement of the powder application apparatus 10″over the carrier 16 in the second moving direction D2 and the abutmentof the second channel opening/closing element 26 b against the secondstopper 28 b causes the first channel opening/closing element 26 a tomove into its first position, in which it allows the discharge of rawmaterial powder from the first powder storage 12 a onto the carrier 16.Simultaneously, the second channel opening/closing element 26 b is movedinto its second position, in which it still prevents the discharge ofraw material powder from the second powder storage 12 b onto the carrier16.

When the first channel opening/closing element 26 a is disposed in itsfirst position, the first channel opening/closing element 26 a projectsfurther from the first side surface 34 a of the housing 36 of the powderapplication apparatus 10″ than in its filling position. The secondchannel opening/closing element 26 b, when being disposed in its secondposition, however, projects less from the second side surface 34 b ofthe housing 36 of the powder application apparatus 10″ than in itsfilling position and in particular is aligned with the second sidesurface 34 b of the housing 36 of the powder application apparatus 10″.

Further, a combined movement of the first and the second channelopening/closing element 26 a, 26 b from their filling position in thesecond moving direction D2 due to a movement of the powder applicationapparatus 10″ over the carrier 16 in the first moving direction D1 andthe abutment of the first channel opening/closing element 26 a againstthe first stopper 28 a causes the first channel opening/closing element26 a to move into its second position, in which it still prevents thedischarge of raw material powder from the first powder storage 12 a ontothe carrier 16. Simultaneously, the second channel opening/closingelement 26 is moved into its first position, in which it allows thedischarge of raw material powder from the second powder storage 12 bonto the carrier 16.

When the first channel opening/closing element 26 a is disposed in itssecond position, the first channel opening/closing element 26 a projectsless from the first side surface 34 a of the housing 36 of the powderapplication apparatus 10″ than in its filling position and in particularis aligned with the first side surface 34 a of the housing 36 of thepowder application apparatus 10″. The second channel opening/closingelement 26 b, when being disposed in its first position, however,projects further from the second side surface 34 b of the housing 36 ofthe powder application apparatus 10″ than in its filling position.

In the embodiment of a powder application apparatus 10′ shown in FIGS. 3a to 3 c, a spring mechanism for pushing the first biasing at least oneof the first and the second channel opening/closing element 26 a, 26 bin either the first or the second moving direction D1, D2 can bedispensed with. Instead, the movement of both, the first and the secondchannel opening/closing element 26 a, 26 b is achieved by theinteraction of the first channel opening/closing element 26 a with thefirst stopper 28 a and the interaction of the second channelopening/closing element 26 b with the second stopper 28 b.

As becomes apparent from FIGS. 3 b and 3 c, at a bottom surface 44 ofthe powder application apparatus 10″, a detachably attached levelingslider 46 is provided. The leveling slider 46 may be exchanged easily ondemand. Between the first powder storage 12 a and the second powderstorage 12 b, a space 48 is provided which extends, starting from thebottom surface 44 of the powder application apparatus 10″, into thepowder application apparatus 10″ towards a first part 20 of the powderapplication apparatus 10″. A holding element 50 is fitted into the space48 such that it is movable along a vertical axis V within the space 48,wherein a bottom surface of the holding element 50 houses the detachablyattached leveling slider 46. The vertical position of the holdingelement 50 is adjustable by micrometer screws 52 extending verticallythrough a top surface 54 of the powder application apparatus 10″ andthrough the space 48, wherein the micrometer screws 52 can be actuatedat their top ends. In this way, a very simple mechanism is providedenabling to easily modify the vertical position of the detachablyattached leveling slider 46. In case the leveling slider 46 is made of asoft, elastic material such as, for example, rubber, the leveling slider46 is received in a suitable recess provided in the holding element 50.In case the leveling slider 46 is made of a hard non-elastic materialsuch as, for example, metal or ceramic, the leveling slider 46 isclamped to the holding element 50 by means of a suitable clampingmechanism.

The leveling slider 46 is arranged between the first and the secondpowder supply channel 14 a, 14 b. Hence, when the powder applicationapparatus 10″ is moved over the carrier 16 in the first moving directionD1, the leveling slider 46 is disposed behind the first powder supplychannel 14 a and thus may distribute raw powder over the carrier 16which has been discharged from the first powder storage 12 a via thefirst powder supply channel 14 a. Similarly, when the powder applicationapparatus 10″ is moved over the carrier 16 in the second movingdirection D2, the leveling slider 46 is disposed behind the secondpowder supply channel 14 b and thus may distribute raw powder over thecarrier 16 which has been discharged from the second powder storage 12 avia the second powder supply channel 14 b.

The first powder storage 12 a extends parallel to a plane 56 beinginclined by a first angle α with regard to a vertical plane 58coinciding with a longitudinal axis 60 of the powder applicationapparatus 10″ such that a distance 64 between the vertical plane 58 andthe first powder storage 12 a increases when moving from the first, i.e.an upper part of the first powder storage 12 a towards a second part ofthe first powder storage 12 a. Further, the second powder storage 12 bextends along a plane 62 being inclined by a second angle β with regardto the vertical plane 58 of the powder application apparatus 10″ suchthat a distance 66 between the vertical plane 58 and the second powderstorage 12 b increases when moving from a first, i.e. an upper part ofthe second powder storage 12 b to a second part of the second powderstorage 12 b. Since the height 68 of the first powder storage 12 a andthe second powder storage 12 b (i.e. a distance between a bottom surface70 and a top surface 72 of the first/second powder storage 12 a, 12 b)is kept small, the volume of the first/second powder storage 12 a, 12 bis also limited which means that the amount of raw powder materialstored in the first powder storage 12 a/in the second powder storage 12b is also limited.

This reduces the weight of the power application apparatus 10″ duringmovement of the power application apparatus over the carrier 16 whichmeans that the moving speed can be increased. On the other hand, sincethere is enough raw material powder in the first powder storage 12 a andthe second powder storage 12 b for generating two powder layers (onewhen moving the power application apparatus towards the first stopper 28a using raw material powder from the first powder storage 12 a, andanother one when moving the power application apparatus 10″ towards thesecond stopper 28 b using raw material powder from the second powderstorage 12 b), no interruption of the powder application process isneeded. It is then sufficient to refill raw material powder into thefirst powder storage 12 a and into the second powder storage 12 b onlyafter two powder layers have been generated.

Like in the first embodiment of a powder application apparatus 10′depicted in FIGS. 2 a and 2 b, also in the powder application apparatus10″ of FIGS. 3 a to 3 c the amount of powder applied onto the carrier 16is controlled by suitably controlling the amount of powder introducedinto the first and the second powder storage 12 a, 12 b. In particular,the first and the second powder storage 12 a, 12 b both are filled withan amount of powder that corresponds to the amount of powder which isnecessary to apply one powder layer onto the carrier 16 plus apredetermined excess powder amount which serves to prevent underfeedingof powder onto the carrier 16.

An inlet end of the first powder storage 12 a comprises a plurality offirst inlets 74 for receiving raw material powder, and an inlet end ofthe second powder storage 12 b comprises a plurality of second inlets 76for receiving raw material powder, wherein the first inlets 74 alternatewith the second inlets 76 other along a direction parallel to thelongitudinal axis 60 of the powder application apparatus 10″. In thisway, it is possible to fill a first powder material into the firstpowder storage 12 a, and to separately fill a second powder materialinto the second powder storage 12 b without having the danger that thedifferent powder materials mix with each other. Thus, sandwich layerstructures of different materials can be generated easily. Since thebottom surfaces 70 of the first powder storage 12 a and the secondpowder storage 12 b are inclined, raw powder material received by thepowder storages 12 a, 12 b slides down along the bottom surfaces 70 in aturbulent-free manner which improves the quality of the powder layersproduced (no or only low generation of powder dust).

If the first inlets 74 or the second inlets 76 are blocked (e.g. by acorresponding plate), only one of the first storage 12 a and the secondpowder storage 12 b is filled with raw material powder. In this way, itis easy to switch between generation of only one powder layer per cycleor two powder layers per cycle.

What is claimed:
 1. A powder application apparatus for use in a devicefor manufacturing work pieces by exposing powder layers toelectromagnetic radiation or particle radiation, comprising: a firstpowder storage provided in a first part of the powder applicationapparatus and configured to receive and store raw material powder, afirst powder supply channel provided in a second part of the powderapplication apparatus and configured to discharge raw material powderfrom the first powder storage onto a carrier located below theapparatus, and a first channel opening/closing element provided in thefirst powder supply channel and configured to be moved between a firstposition in which the first channel opening/closing element allows thedischarge of raw material powder from the first powder storage onto thecarrier, and a second position in which the first channelopening/closing element prevents the discharge of raw material powderfrom the first powder storage onto the carrier, wherein the firstchannel opening/closing element is configured to be moved between thefirst and the second position by means of an external mechanical forceacting on the first channel opening/closing element, the externalmechanical force being caused by abutting the first channelopening/closing element against a stopper of the device formanufacturing work pieces when moving the powder application apparatusover the carrier.
 2. The powder application apparatus according to claim1, wherein, in one of the first and the second position, the firstchannel opening/closing element projects from a side surface of ahousing of the powder application apparatus, and wherein, in the otherone of the first and the second position, the first channelopening/closing element does not project from the side surface of thehousing of the powder application apparatus, or projects less or furtherfrom the side surface of the housing of the powder applicationapparatus.
 3. The powder application apparatus according to claim 2,wherein the first channel opening/closing element is a plate membermovable in a horizontal direction between the first and the secondposition, wherein, in one of the first and the second position, a sidesurface of the plate member projects from the side surface of thehousing of the powder application apparatus, and wherein, in the otherone of the first and the second position, the side surface of the platemember is aligned with the side surface of the housing of the powderapplication apparatus or projects less or further from the side surfaceof the housing of the powder application apparatus.
 4. The powderapplication apparatus according to claim 1, further comprising: a secondpowder storage provided in a first part of the powder applicationapparatus and configured to receive and store raw material powder, asecond powder supply channel provided in a second part of the powderapplication apparatus and configured to discharge raw material powderfrom the second powder storage onto the carrier located below theapparatus and a second channel opening/closing element provided in thesecond powder supply channel and configured to be moved between a firstposition in which the second channel opening/closing element allows thedischarge of raw material powder from the second powder storage onto thecarrier, and a second position in which the second channelopening/closing element prevents the discharge of raw material powderfrom the second powder storage onto the carrier, wherein the secondchannel opening/closing element is configured to be moved between thefirst and the second position by means of an external mechanical forceacting on the second channel opening/closing element, the externalmechanical force being caused by abutting the second channelopening/closing element against a stopper of the device formanufacturing work pieces when moving the powder application apparatusover the carrier.
 5. The powder application apparatus according to claim4, wherein the first channel opening/closing element and the secondchannel opening/closing element are formed integrally with each other.6. The powder application apparatus according to claim 5, wherein thefirst and the second channel opening/closing element are configured suchthat both, the first and the second channel opening/closing element, canbe simultaneously positioned in a filling position, in which theyprevent the discharge of raw material powder from the first and thesecond powder storage onto the carrier.
 7. The powder applicationapparatus according to claim 5, wherein the first and the second channelopening/closing element are configured such that a combined movement ofthe first and the second channel opening/closing element from theirfilling position in a first moving direction causes the first channelopening/closing element to move into its first position, in which itallows the discharge of raw material powder from the first powderstorage onto the carrier, and simultaneously causes the second channelopening/closing element to move into its second position, in which itprevents the discharge of raw material powder from the second powderstorage onto the carrier.
 8. The powder application apparatus accordingto claim 5, wherein the first and the second channel opening/closingelement are configured such that a combined movement of the first andthe second channel opening/closing element from the filling position ina second moving direction causes the first channel opening/closingelement to move into its second position, in which it prevents thedischarge of raw material powder from the first powder storage onto thecarrier, and simultaneously causes the second channel opening/closingelement to move into its first position, in which it allows thedischarge of raw material powder from the second powder storage onto thecarrier.
 9. The powder application apparatus according to claim 4,wherein the first powder storage extends along a plane being inclinedwith regard to a vertical plane coinciding with a longitudinal axis ofthe powder application apparatus such that a distance between thevertical plane and the first powder storage increases when moving froman inlet part of the first powder storage to an outlet part of the firstpowder storage.
 10. The powder application apparatus according to claim4, wherein the second powder storage extends along a plane beinginclined with regard to the vertical plane of the powder applicationapparatus such that a distance between the vertical plane and the secondpowder storage increases when moving from an inlet part of the secondpowder storage to an outlet part of the second powder storage.
 11. Thepowder application apparatus according to claim 4, wherein an inlet endof the first powder storage comprises a plurality of first inlets forreceiving raw material powder, and wherein an inlet end of the secondpowder storage comprises a plurality of second inlets for receiving rawmaterial powder, wherein the first inlets are different from the secondinlets.
 12. The powder application apparatus according to claim 11,wherein the first inlets and the second inlets alternate with each otheralong a direction parallel to the longitudinal axis of the powderapplication apparatus.
 13. The powder application apparatus according toclaim 4, wherein, at a bottom surface of the powder applicationapparatus, a detachably attached leveling slider is provided.
 14. Thepowder application apparatus according to claim 4, wherein, between thefirst powder storage and the second powder storage, a space is providedwhich extends, starting from a bottom surface of the powder applicationapparatus, into the powder application apparatus towards the first partof the powder application apparatus, wherein a holding element is fittedinto the space such that it is movable along a vertical direction withinthe space, wherein a bottom surface of the holding element comprises adetachably attached leveling slider.
 15. The powder applicationapparatus according to claim 14, wherein the vertical position of theholding element is adjustable by micrometer screws extending verticallythrough a top surface of the powder application apparatus and throughthe space so that the micrometer screws can be actuated at their topends.
 16. A method of manufacturing work pieces by exposing powderlayers to electromagnetic radiation or particle radiation using a powderapplication apparatus comprising: a first powder storage provided in afirst part of the powder application apparatus and configured to receiveand store raw material powder, a first powder supply channel provided ina second part of the powder application apparatus and configured todischarge raw material powder from the first powder storage onto acarrier located below the apparatus, and a first channel opening/closingelement provided in the first powder supply channel and configured to bemoved between a first position in which the first channelopening/closing element allows the discharge of raw material powder fromthe first powder storage onto the carrier, and a second position inwhich the first channel opening/closing element prevents the dischargeof raw material powder from the first powder storage onto the carrier,wherein the method comprises: moving the first channel opening/closingelement between the first and the second position by means of anexternal mechanical force acting on the first channel opening/closingelement, the external mechanical force being caused by abutting thefirst channel opening/closing element against a stopper of the devicefor manufacturing work pieces when moving the powder applicationapparatus over the carrier.
 17. The method according to claim 16,wherein the powder application apparatus further comprises: a secondpowder storage provided in a first part of the powder applicationapparatus and configured to receive and store raw material powder, asecond powder supply channel provided in a second part of the powderapplication apparatus and configured to discharge raw material powderfrom the second powder storage onto the carrier located below theapparatus, and a second channel opening/closing element provided in thesecond powder supply channel and configured to be moved between a firstposition in which the second channel opening/closing element allows thedischarge of raw material powder from the second powder storage onto thecarrier, and a second position in which the second channelopening/closing element prevents the discharge of raw material powderfrom the second powder storage onto the carrier, wherein the methodfurther comprises: moving the second channel opening/closing elementbetween the first and the second position by means of an externalmechanical force acting on the second channel opening/closing element,the external mechanical force being caused by abutting the secondchannel opening/closing element against a stopper, the first channelopening/closing element allows the discharge of the device formanufacturing work pieces when moving the powder application apparatusover the carrier.
 18. The method of claim 16, further comprising atleast one of the steps: simultaneously positioning both, the first andthe second channel opening/closing element in a filling position, inwhich they prevent the discharge of raw material powder from the firstand the second powder storage onto the carrier, moving both, the firstand the second channel opening/closing element, from their fillingposition in a first moving direction so as to cause the first channelopening/closing element to move into its first position, in which itallows the discharge of raw material powder from the first powderstorage onto the carrier, and to simultaneously cause the second channelopening/closing element to move into its second position, in which itprevents the discharge of raw material powder from the second powderstorage onto the carrier, and moving both, the first and the secondchannel opening/closing element from the filling position in a secondmoving direction so as to cause the first channel opening/closingelement to move into its second position, in which it prevents thedischarge of raw material powder from the first powder storage onto thecarrier, and to simultaneously cause the second channel opening/closingelement to move into its first position, in which it allows thedischarge of raw material powder from the second powder storage onto thecarrier.